1. Field of the Invention
The invention relates to an exhaust gas purifying apparatus in the following: exhaust gas purifying apparatus, and particularly to a structure of a particulate filter as a component of an exhaust gas-purifying apparatus.
2. Description of the Related Art
A particulate filter for collecting particulates in the exhaust gas discharged from an internal combustion engine is disclosed in published Japanese translation of PCT-application, JP-T-8-508199. In this particulate filter, a honeycomb structural body is made of a porous material. Among a plurality of passages in this honeycomb structural body (hereinafter referred to as filter passages), some of the filter passages are closed with plugs at their upstream ends whereas the remaining filter passages are closed with plugs at their downstream ends, so that the exhaust gas flowed into the particulate filter always passes the walls which forms the filter passages (hereinafter referred to as filter partitioning walls) without fail and then flows out of the particulate filter.
ID this particulate filter, since the exhaust gas always passes the filter partitioning walls without fail and then flows out of the particulate filter, its particulate collection rate is higher than the particulate collection rate of a particulate filter in which the exhaust gas only passes the filter passages without passing the partitioning walls of the particulate filter.
In the particulate filter described in the aforementioned Patent Publication, the filter passages are closed by combining the end portions of the filter partitioning walls together and then by connecting these end portions with each other. As a result of this structure, the exhaust gas inlet openings of the filter passages are shaped into the form of a funnel. According to the structure wherein the exhaust gas inlet openings of the filter passages are shaped into the form of a funnel as in the manner described above, the exhaust gas smoothly flows into the filter passages without causing turbulence. In other words, when the exhaust gas flows into the filter passages, the exhaust gas never turns into turbulence. For this reason, the pressure loss in the particulate filter described in this Patent Publication is low.
Meanwhile, in the particulate filter described above, the top ends of the combined partitioning walls are sharply pointed. Therefore, for example, when the particulate filter is handled in order to install the particulate filter in the exhaust passage of the internal combustion engine, if these combined partitioning walls are brought into contact with the parts and the like of the internal combustion engine, the top ends of the combined partitioning walls become chipped.